how to find magnitude of net force

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In mechanics, the net force (also known as resultant force) is the overall force acting on an object when all the individual forces acting on the object are added together.

Informal introduction

A force in mechanics is a concept that has both a size and a direction. The net force acting on an object is the sum of the forces onto the object, taking into account both their sizes, and their directions. For example, if an object has two forces acting on it, with equal sizes but in opposite directions, then the net force will be zero (technically: a null vector). If instead the forces are of equal size and in the same direction, then the net force is equal to twice either force. The net force can be seen as a hypothetical force that, acting on an object, has the same effect as all the actual forces combined.

Definition

The net force Fnet = F1 + F2 + â€¦ is a vector produced when two or more forces { F1, F2, â€¦ } act upon a single object. It is calculated by vector addition of the force vectors acting upon the object.

Examples

When force A and force B act on an object in the same direction (parallel vectors), the net force (C) is equal to A + B, and points in the same direction as A and B.

When force A and force B act on an object in opposite directions (180 degrees between then - anti-parallel vectors), the net force (C) is equal to |A - B|, and points in the direction of whichever one has greater absolute value ("greater magnitude").

(Note: The illustration assumes that the object, in this case a square, has no center of mass and can be treated like apoint.)

When the angle between the forces is anything else, then the net force can be visualized using the parallelogram rule.

For example, see Figure 3. This construction has the same result as moving F2 so its tail coincides with the head of F1, and taking the net force as the vector joining the tail of F1 to the head of F2. This procedure can be repeated to add F3 to the resultant F1 + F2, and so forth. Figure 4 is an example.

From Yahoo Answers

Question:A gun is fired and a 50g bullet is accelerated to a muzzle speed of 100 m/s. If the length of the gun barrel is .90m what is the magnitude of the accelerating force, assuming the acceleration is constant??? Can somebody please explain this in simple terms?

Answers:Basically, here's what you're given:
mass of the bullet: 50g
final velocity: 100 m/s
initial velocity: 0 m/s (the bullet is at rest before the gun is fired)
displacement: 0.90 m
You want to find acceleration. We also know that (final velocity)^2=(2*displacement*acceleration)+(initial velocity)^2. So (100)^2=2(.9)(x)+0^2
10000=1.8x
5555.55 m/(s^2)=a
However, if your teacher cares about significant figures (and most do), your answer would be 6,000 m/s^2=a
I hope that helped!

Question:If the balls mass is 47 g find the magnitude of its average acceleration while the force is applied a golf ball is given 114J of energy by a golf club that exerts a force over a distance of 4.4 cm while the club and the ball are in contact. If the balls mas is 47g find the magnitude of its average acceloartion while the force is applied.

Answers:Your question does not contain enough information to find the average acceleration in this case.
A general technique for finding an average force would be to integrate the actual force or acceleration over the desired period and then divide by the interval. In many cases this is a simple linear average and easy to calculate. The acceleration may be given explicitly or it may be calculated as force divided by mass.
Another approach is to determine the total work done by some other means such as a change in potential energy and use that to determine the average force that would have been required to expend that amount of work. Work done is force times distance and is equal to the net change in energy of the system. If the mass is constant then the average acceleration is just the average force divided by the mass.

Question:Two trucks on opposite sides of a river, are used to pull a barge along a straight river. They are connected to the barge at one point by ropes of equal length. The angle between the two ropes is 50 degrees. Each truck is pulling with a force of 1500 Newtons.
Find the magnitude and direction of the force acting on the barge.
How do I do this???????

Answers:You can always do it graphically. Make a scale, such as 500 N=1 cm. Then, draw one 3 cm line thats horizontal. Draw another line thats 50 degrees to the 1st line, making that 3 cm as well. Then, you make it a parallelogram, connecting the opposide corners together. You measure the magnitude and degree with that.
this is how you do it:
http://tinypic.com/view.php?pic=ri8z7k&s=5
the picture isnt to scale, its just to explain what i said better.

Question:The elevator and passengers have a mass of 5500 kg. After a stop at the thirteenth floor, the elevator accelerates upward uniformly at 1.0 m/s^2 until it is rising at 2.0 m/s. What is the magnitude of the net force acting on the elevator as it accelerates?

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